This chapter reviews the various approaches to energy auditing and outlines a standard approach to organizing and conducting an energy audit. An energy audit can be simply defined as a process of determining the types and costs of energy use in the building, evaluating where a building or plant uses energy, and identifying opportunities to reduce consumption. In most facilities, companies, and other corporate settings, upgrades to a facility’s energy infrastructure must compete for capital funding with non-energy-related investments. In 2006, the Certified Energy Auditor and Certified Energy Auditor in Training certifications were developed and added to the impressive portfolio of certifications offered by the Association of Energy Engineers. Pre-site work is important in getting to know basic aspects of the building. The amount of time required will vary depending on the completeness of the pre-site information collected, the complexity of the building and systems, and the need for testing of equipment.